money=1000
while true
do
    echo  "######################"
    echo  "1. 存款"
    echo  "2. 取款"
    echo  "3. 查看余额"
    echo  "4. 退出"
    echo  "######################"
    read -p "请根据菜单输入数字:" num
    case  $num  in
    1)
    clear
    read -p "请把钱放置 ATM机的取款口:" a
    conut=`expr $money + $a`
    echo "总额度: $conut"
    continue
    ;;
    2)
    read -p "请输入取款金额:" b
    conut=`expr $money - $b`
    echo "当前余额:"$conut
    continue
    ;;
    3)
    echo  "余额："$conut
    continue
    ;;
    4)
    exit
    ;;
    *)
    echo "输入错误"
    break
    ;;
    esac
done